Elevator mechanism and method

ABSTRACT

An elevator mechanism and method for raising and lowering radioactive samples through a vertical well which has a practical limit on its height. The elevator mechanism adds little or nothing to the height of the well by using an elongated flexible metal member such as tape secured to the bottom of the elevator platform and extending downwardly through the well, where the tape is bent laterally for connection to a drive means. In the particular embodiment illustrated, the tape is bent laterally below the bottom shielding for the counting chamber in a scintillation detector, and then upwardly along or through one side of the shielding to a reel at the top of the shielding. The tape is wound onto the reel, and the reel is driven by a reversible motor which winds and unwinds the tape on the reel to raise and lower the elevator platform.

United States Patent [191 Frank [451 Sept. 16, 1975 1 ELEVATOR MECHANISMAND METHOD [75] Inventor: Edmund Frank, Chicago, Ill.

[73] Assignee: Packard Instrument Company, Inc.,

Downers Grove, Ill.

[22] Filed: Jan. 12, 1973 [21] Appl. No.: 322,965

Related U.S. Application Data [60] Division of Ser. No. 241,987, April7, 1972,

abandoned, Continuation-impart of Ser. No. 368,693, June 11, 1973.

[52] U.S. Cl. 187/17; 187/1; 52/108 [51] Int. Cl B66b 11/04 [58] Fieldof Search 187/27, 20, 17, 3, 1, 4,

Primary ExaminerRichard A. Schacher Assistant Exuminer]ames L. RowlandAttorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[ 5 7 1 ABSTRACT An elevator mechanism and method for raising andlowering radioactive samples through a vertical well which has apractical limit on its height. The elevator mechanism adds little ornothing to the height of the well by using an elongated flexible metalmember such as tape secured to the bottom of the elevator platform andextending downwardly through the well, where the tape is bent laterallyfor connection to a drive means. In the particular embodimentillustrated, the tape is bent laterally below the bottom shielding forthe counting chamber in a scintillation detector, and then upwardlyalong or through one side of the shielding to a reel at the top of theshielding. The tape is wound onto the reel, and the reel is driven by arevers ible motor which winds and unwinds the tape on the reel to raiseand lower the elevator platform.

5 Claims, 4 Drawing Figures HEET 1 0 2 PATENTEBSEP 1 61975 ELEVATORMECHANISM AND METHOD RELATED APPLICATIONS The present application is adivisional application based upon my copending parent application Ser.No. 241,987, filed April 7, 1972 and entitled "Elevator Mechanism forScintillation Detectors and the Like now abandoned in favor of mycopending continuationin-part application Ser. No. 368,693, filed Junell,v

1973 and entitled Elevator Mechanism and Method for ScintillationDetectors".

The present invention relates generally to elevator mechanisms andmethods and. more particularly, to elevator mechanisms that can be usedto raise and lower items through a vertical well.

It is a primary object of the present invention to provide an improvedelevator system that raises and lowers an elevator platform by forcesapplied to the bottom of the platform, and yet requires little or nospace beneath the well traversed by the elevator platform.

Another object of the invention is to provide an improved elevatormechanism of the foregoing type which is particularly suitable forraising and lowering samples in a benchtop instrument, where the heightof the instrument must be kept as small as possible. In this connection,a more specific object of the invention is to provide such an improvedelevator mechanism which can be used to raise and lower items through avertical well, which has a certain minimum height even without theelevator mechanism.

It is a further object of the invention to provide an improved elevatormechanism of the type described above which requires only a small numberof parts and can be efficiently manufactured at high production ratesand a relatively low cost.

Yet another object of the invention is to provide such an improvedelevator mechanism which provides reliable operation over a longoperating life, with a minimum of maintenance.

A still further object of the invention is to provide such an improvedelevator mechanism which permits the use of a simple. conventional primemover in the drive mechanism.

Other objects and advantages of the invention will be apparent from thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a top plan view of a scintillation detector embodying theinvention;

FIG. 2 is a side elevation of the detector of FIG. 1, with a fragment ofthe central portion thereof broken away to show the internal structure;

FIG. 3 is an enlarged perspective view of the elevator mechanism forraising and lowering samples in the detector of FIG. 1; and

FIG. 4 is an enlarged section taken substantially along the line 44 inFIG. 3.

While the invention will be described in connection with certainpreferred embodiments. it is to be understood that the invention is notlimited to these particular embodiments. On the contrary, it is intendedto cover all alternatives. modifications and equivalent arrangements asmay be included within the spirit and scope of the invention.

Turning now to the drawings and referring first to FIGS. 1 and 2, aplurality of radioactive samples contained in vials 10 are advanced inseriatium order past a fixed counting station 11. In the particulararrangement illustrated. the sample vials 10 are carried in verticalcompartments formed by a flexible belt 12 forming vial compartmentswhich are open at both the top and the bottom. Each time a sample vialis advanced into alignment with the counting station 11, as determinedby a sensing switch 13, the aligned vial rests on an elevator platform14 which automatically lowersthe sample vial through a vertical tube14:: and liner 14h into a counting chamber 15 where the radioactivity ofthe sample is automatically measured.

In a detector of the type illustrated. the counting chamber 15 istypically designed to measure gamma radiation by means of a pair ofthallium-activated sodium iodide crystals 16 and 17 forming oppositesides of the counting chamber and mounted on a corresponding pair oflight-sensing photomultiplier tubes 18 and 19, respectively. As is wellknown, the gamma radiation produces light scintillations in the crystals16 and 17, and these scintillations are converted to correspondingvoltage pulses by means of the photomultipliers l8 and 19. The energylevel of the gamma rays is determined by the intensity of the lightscintillations and the amplitude of the corresponding voltage pulses,while the rate at which the gamma rays are emitted is determined by thefrequency of the light scintillations and the corresponding voltagepulses.

In order to shield the counting chamber and particularly the crystals 16and 17 from background radiation from extraneous sources, the crystalsare housed in a non-magnetizable container 20 which is held in place bya pair of clamping frames 2011 within an elongated core structure 20hthat is shielded on all sides by means of a plurality of lead blocks 21contained within the external housing 22. This lead shielding makes thedetector relatively bulky, and thus it is desirable to minimize the sizeof the sample transfer mechanism in order to make the overall size ofthe detector as small as possible. This is particularly true of theelevator mechanism which must move the successive samples along avertical path of substantial length in order to traverse the relativelythick lead shielding above the counting chamber. This problem ofminimizing the overall size of the detector, including the elevatormechanism, is particularly acute in the case of scintillation detectorswhich are intended for benchtop use.

In accordance with the present invention, the elevator mechanismincludes an elongated flexiable metal member such as a metal tapesecured to the bottom of the elevator platform 14 and extendingdownwardly through the counting chamber and the lead shieldingthereunder, the tape having sufficient flexibility to enable it to bebent through or around the sheilding below the counting chamber andwound onto a reel which is selectively rotated in both directions forraising and lowering the elevator platform. The flexible tape isunsupported along the path traversed by the elevator platform, but hassufficient rigidity to support the platform throughout the entire lengthof the vertical path traversed by the platform. Thus, in theillustrative arrangement, an elongated metal tape 30 is secured to thebottom of the elevator platform 14 and extends downwardly throughregistered apertures formed in the shielding blocks 21 disposed belowthe counting chamber l5. One of the lead shielding blocks 21a holds apair of bearing pads 31 and 32 for supporting and guiding the tape 30 asit passes back and forth through the bottom shielding. Directly beneaththe bearing pads 31 and 32, the tape 30 enters a generally U-shaped tapeguide 33 having a short vertical leg 33a aligned with the elevator axisand a long vertical leg 33h extending up through one side of the leadshielding 21.

In order to minimize the vertical dimension of the elevator mechanism,the tape guide 33 bends the tape 30 horizontally directly beneath thelead shielding so that the tape extends transversely away from thevertical axis of the elevator. and the guide 33 then bends the tapevertically up through a side portion of the lead shielding to a reel 34.The reel 34 is driven by a reversible electric motor 35 via sprocket 36on the motor shaft and a chain 37 meshing with the sprocket 36 and asecond sprocket 38 fixed to the reel shaft 39. As the reel is rotated inthe counterclockwise direction as viewed in FIG. 3. the tape 30 isadvanced upwardly through the counting chamber to raise the elevatorplatform 14 to its raised position at the top of the housing 22, asillustrated in broken lines in FIG. 2. When the reel is driven in theclockwise direction as viewed in FlG. 3, the tape is lowered through thecounting chamber 15 to position a sample vial carried by the elevatorwithin the counting chamber. A preferred control system for energizingand de-energizing the motor in alternating directions to control thewinding and unwinding of the tape 30 on the reel 34, thereby controllingthe lowering and raising of the elevator platform, is described indetail in my eopending application Ser. No. 241.988. filed Apr. 7. I972.entitled Method And Apparatus For Optimizing Measurement OfRadioactivity Of Samples ln Scintillation Type Counter". now U.S. Pat.No. 3.786.259. assigned to the same assignee as the present invention.

In order to provide the exemplary elevator tape 30 with sufficientrigidity to support the elevator platform throughout the entire lengthof its vertical travel. the tape 30 is curved in the directiontransverse to its direction of movement. Thus. as shown most clearly inFIG. 4. the tape 30 is curved transversely of its longitudinal axis toprovide the tape with rigidity along its longitudinal axis. While thistransverse curve makes the tape rigid enough to support the weight ofthe elevator platform 14 and a sample vial carried thereon. the tape isstill sufficiently flexible to permit it to be bent around the cornersformed by the tape guide 33 and to be wound onto the reel 34.Consequently. the vertical dimension of the entire elevator assembly canbe made extremely compact. so that it adds very little to the totalheight of the complete spectrometer.

Referring to FIG. 3 for a more detailed description of the tape guide33, the main body portion of the guide 33 is formed by a pair ofrelatively thin elongated strips 40 and 41 positioned on opposite sidesof a pair of spacers 42 and 43 extending along the longitudinal edges ofthe strips 40 and 41 and connected thereto by a plurality ofbolts 44 andnuts 45. The transverse space between the two spacers 42 and 43 forms acentral cavity for supporting and guiding the tape 30 along thegenerally U-shaped path defined by the complete guide assembly 33. Aguide strip 46 is provided on the inside surface of the body strip 40 toprovide a bearing surface for the longitudinal edges of the curve tape30.

In accordance with one particular aspect of the invention. a pluralityof roller bearings are mounted on the tape reel 34 and spaced around thecircumference thereof for holding the tape in a compact coil on the reel34. Thus, as shown in FIG. 3 six roller bearings 50 are mounted atequally spaced positions around the reel 34 with their axes parallel tothe axis of the reel to hold that portion of the tape that is wound onthe reel in the form of a circular coil. The spring action of the tape30 continuously urges the tape toward a straight longitudinalconfiguration, and thus biases the tape that is wound onto the reel 34outwardly against the roller bearings 50.

To mount the tape guide 33 on the lead shielding or its outside housing22, a pair of mounting brackets 52 and 53 are secured to the body strip41 at opposite ends thereof. Suitable screws or other conventionalfastening elements are passed through holes in these mounting flanges 52and 53 to fix both ends of the guide assembly to adjacent portions ofthe lead blocks 21 or the housing 22.

As can be seen from the foregoing detailed description. this inventionprovides an improved elevator mechanism and method that raises andlowers the elevator platform by applying forces to the bottom of theplatform. and yet the entire elevator mechanism requires little or nospace beneath the well traversed by the elevator platform. Thus. theelevator mechanism provided by this invention is particularly suitablefor use in benchtop instruments. where the height of the instrument mustbe kept as small as possible. The eleva tor mechanism is also ideallysuited for use in raising and lowering radioactive samples through ashielded vertical counting chamber in a scintillation detector. whichhas a minimum height even without the elevator mechanism due to theshielding required above and below the counting chamber. Furthermore.this improved elevator mechanism requires only a small num ber of partsand can be efficiently manufactured at high production rates and arelatively low cost. and yet its simplicity ensures reliable operationover a long operating life with a minimum of maintenance.

I claim as my invention:

1. An elevator mechanism for raising and lowering items in a verticalwell. said elevator mechanism comprising the combination of a platformmounted for vertical movement through said well, an elongated flexiblemember having only one end secured to only the bottom of said platformand extending downwardly from said platform through said well. laterallyaway from said well below the bottom thereof, and then upwardly withsaid flexible member terminating with its other end at an elevationabove said well. said flexible member being unsupported along the lengthof travel of said platform and sufficiently rigid to support saidplatform throughout said length of travel. said flexible member alsobeing sufficiently flexible to be bent about the bottom of said well.and reversible drive means connected to said other flexible member endfor advancing and retracting said member to raise and lower saidplatform in said well.

2. An elevator mechanism as set forth in claim 1 wherein said elongatedflexible member is a metal tape.

3. The elevator mechanism as set forth in claim 1 in which said drivemeans includes a reel to which said other flexible member end is coupledand upon which said flexible member may be wound and unwound byactuation of said drive means.

4. A method of raising and lowering items in a verti cal well having aplatform mounted for vertical movement within the well. said methodcomprising the steps out said length of travel. coupling said otherflexible member end to a reversible drive mechanism. and alternatelyactuating said drive mechanism for advancing and retracting said memberto raise and lower said platform within said well.

5. A method of raising and lowering items in a vertical well as setforth in claim 4 wherein said elongated flexible member is a metal tape.

n a :u

1. An elevator mechanism for raising and lowering items in a verticalwell, said elevator mechanism comprising the combination of a platformmounted for vertical movement through said well, an elongated flexiblemember having only one end secured to only the bottom of said platformand extending downwardly from said platform through said well, laterallyaway from said well below the bottom thereof, and then upwardly withsaid flexible member terminating with its other end at an elevationabove said well, said flexible member being unsupported along the lengthof travel of said platform and sufficiently rigid to support saidplatform throughout said length of travel, said flexible member alsobeing sufficiently flexible to be bent about the bottom of said well,and reversible drive means connected to said other flexible member endfor advancing and retracting said member to raise and lower saidplatform in said well.
 2. An elevator mechanism as set forth in claim 1wherein said elongated flexible member is a metal tape.
 3. The elevatormechanism as set forth in claim 1 in which said drive means includes areel to which said other flexible member end is coupled and upon whichsaid flexible member may be wound and unwound by actuation of said drivemeans.
 4. A method of raising and lowering items in a vertical wellhaving a platform mounted for vertical movement within the well, saidmethod comprising the steps of connecting only one end of an elongatedflexible member to only the bottom of said platform and extending saidflexible member downwardly from said platform through said well,laterally away from said well below the bottom thereof, and thenupwardly so that the other end of said flexible member is at anelevation above said well, said flexible member being unsupported alongthe length of travel of said platform and sufficiently rigid to supportsaid platform throughout said length of travel, coupling said otherflexible member end to a reversible drive mechanism, and alternatelyactuatIng said drive mechanism for advancing and retracting said memberto raise and lower said platform within said well.
 5. A method ofraising and lowering items in a vertical well as set forth in claim 4wherein said elongated flexible member is a metal tape.